Standard Size Hard Drives?

Im trying to go the cheap route and avoid laptop hard drives. Is this wise? I dont think it would make a huge impact even over time... Yeah so laptop portables are designed for this. But I dont mind if 2 years from now my drive takes a **** from abuse if it save me a lil at setup... Also I plan to position the drives in a sidewise position to avoid from the heads crashing onto the cylinders.

I think it would be just fine. I had a 5.25" BIGFOOT TX in my car mounted vertically for six months. Still has no bad sectors to this day. I've dropped on the floor and it still runs. Now, that is a very good hard drive. Large capacity 3.5" drives these days are a lot pickier.